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Attorney General Jeff Sessions is sworn in to testify before the Senate Judiciary Committee on Capitol Hill in Washington, Oct. 18, 2017.

Attorney General Jeff Sessions rejected a proposal by a junior campaign aide who offered to use his "Russian contacts" to try to set up a meeting between Donald Trump and Vladimir Putin, a source familiar with the matter told NBC News.

Former Trump campaign aide George Papadapoulos, has pleaded guilty to lying to the FBI, and documents released Monday show he was in contact with Russians who offered him "dirt" — including thousands of emails — on Hillary Clinton, NBC News reported.

This revelation is a significant one, because Sessions told Congress under oath in June that he had "no knowledge" of any conversations by anyone connected to the Trump campaign about "any type of interference with any campaign" by Russians.

In a letter to Sessions on Thursday, Sen. Al Franken, the Minnesota Democrat, accused him of failing "to tell the truth about your interactions with Russian operatives during the campaign."

Sessions' spokesperson did not immediately respond to a request for comment about the Franken letter.